Absorptive glass



' ABsoRPTIvE GLASS Filed Maoh 25, 1938 1N V ENIDR. EaBERT H. MILL-s R BYfj r A RNEYS.

QfPaYtentec-ltNo-VQZLG; 41940 I. r 2,223,111,841?f? 2;22s,11s fAsonr'rrim GLASSy YRobert A. Miller, Tarentum, Pa., assigner to Pitts-`.burgh'llate Glass C'ompany, Allegheny County,

Pa. a, corporation'of Pennsylvania Application MarchZ, 1938, Serial No.198,044

2 claims.' (c1. 25o-108) The invention relates to absorptive glass.,that is; glass havingthe property of absorbing or interV rupting theshortery actinic rays, such asv ultra- Evioletrays and X-rays.'Suchfglass is used as a @protection from X-ray machines, for covering'documents to prevent fading-ofthe inkand'for 3 glazingworkWhere-protection of valuable fabrics Y from fading is necessary. 'Ihemostl effective of v y these protective glasses is leadvglass which isused 10. exclusively for X-ray work and in most cases for y'theprotectionof documents. One serious objection to this glass, notheretofore overcome, is"

` ythe tendency of the glass to Weather and tarnish -v and lose itstransparency due to abrasion 15' cleaning, as the glass is soft andsubject to re- 9 V.action with certain yelementsin the atmosphere.

'I'he present invention is designed to ,overcome f this difficulty,4 notonly withordinarylead'glass,

y j violet and X-ray cut-offproperties, such as the lead glasses havinga barium content, which are l Q glass havingv good Aweatheringqualities. The 'i 'most suitable glassl vfor this surface protection ofy, lthe `faces of the .absorptive sheet is ordinary f3 'window glass ofthe thicknessknown as photo y30 glass. 'I'his is a lime soda glass witha high silical rcontent which is hard and strong. Such glass will notvtarnish or weather and, because of its hardness, is not subject toalossof transparency, due

. to an impairment of itspolish, as 'a result of the of the improvedglass is shown in the accompanying-drawing;wherein:v n t f the thicknessof the layers somewhat exaggerated for clearness of illustration.

This photo glass isbetween a sixteenth and a 45 r.thirty-second of aninch in thickness, andfthe y suitable cement, not subject todiscoloration by exposure to light, such as vinylV acetal resin. Asidefrom the protection from weatheringl due cement layers 3, 3', addmaterially to the strength of the sheet, thus reducing the danger ofbreakage glass.. v As an example of the lead glass composition for 1K5'but also with other glasses having high ultran.

subject to the same 'difliculty as to weathering' l and tarnishing.Briefly stated, this result is accomplished by cementing to each face ofthe sheet of absorptive glass a thin sheetl of non-absorptive .abrasionincident to repeated cleaning. 'A' plate f. The figure is a sectionthrough theplatewith Referring to the drawing, the central sheet 'l is nof absorptive glass, such as leadglass, and 2, 2 are n l, sheets of limesoda glass,l such as, photo glass.y

sheets are secured together by the layers 3,13-of a y :'50 to the sheetsz, 2, the use of such sheets and of the l' 1 #in handling and linservice. When the plate is "used for glazing Windows orfor theprotection-cf documents, the sheet I will ordinarily-loe of quarter inchglass, while in X-ray work this thickness maybe asgreatas an inch orleven g more. f

; The use of a drawn glass; such as the photo glass, is preferredfor thefacing sheetsv 2, 2, as;

yopposed. to ground and polished'plate glass, since it is difficult toproduce ground and polished sheets of the desired thinness, and thephoto glass 10 is considerably. stronger than plate glass of the samethickness, as fthe surface layers of drawnv glass are stronger than thesurface layers ofplate` vthe sheet I, the following is typical: y j Percent silicon dioxide -..1 -1 --.134:18

Lead oxide v 1 v 60.3520y Potassium. oxide U +1.52r Antimcny'oxide l .35

Other glasses in the same class arefset forth `25v inthe patent toFrederick Gelstharp No. 2,025,099.A offDecember 25,1935.-` f t l`WhatIclaimis: fv,

V1. In -a laminated glass unit having lcapacityV to absorb ultra-violetrays and X,rays, anL inter- 30 y' mediate glass plate readily subject toinjury upon exposure to weather and having ahighleadoxide v content torender it relatively opaque to said rays,

and a glass sheet cemented on each side'of saidv "k' vintermediate glassplate and .having a high lime 35 content rendering f it relativelyvhard'in` texture, I

and transparent means celnenting-` the glass sheets to the plate wherebya thin transparent protective Y l covering is provided upon each face ofthe thicker 50 intermediate glass plate. v Y

. l ROBERT A. MILLER.

